Ambient temperature compensated overload relay



Dec. 17, 1968 B. D1 MARCO 3,417,358

AMBIENT TEMPERATURE COMPENSATED OVERLOAD RELAY Filed Sept. 22, 1966United States Patent O 3,417,358 AMBIENT TEMPERATURE COMPENSATEDOVERLOAD RELAY Bernard Di Marco, Lincoln Park, Mich., assignor to I-T-ECircuit Breaker Company, Philadelphia, Pa., a corporation ofPennsylvania Filed Sept. 22, 1966, Ser. No. 581,246 8 Claims. (Cl.337-99) ABSTRACT F THE DISCLOSURE In an -overload relay employing laprimary bimetallic element for tripping the contacts of the relay openin the event of a current overload, the primary bimetal operates upon -amotion translator bar which is also acted upon by one leg of a U-shapedambient temperature compensating auxiliary bimetal; the auxiliarybimetal is mounted by the web of its U to a pivotal mounting whichpermits pivoting of the bimetal with respect to the housing; upon anincrease in the ambient temperature in the housing, the auxiliarybimetal legsdeect outward, and the second leg strikes an abutment on thehousing, whereby only the first leg -thereof can deflect outward and thedeflection of the second leg is absorbed by the pivoting of theauxiliary bimetal around its pivot mounting; upon a decrease in theambient temperature, the legs of the auxiliary bimetal move inward,until the second leg of the auxiliary bimetal contacts the over centerspring of the movable contact operating mechanism; thereafter, the sec--ond leg is held stationary while the first leg continues to deflectinward, the deflection of lthe second leg being absorbed through thepivoting of the auxiliary bimetal around its pivot; upon translation ofthe translator bar due to deflection of the primary bimetal as a resultof an overload, the auxiliary bimetal is pivoted by the movement of thetranslator bar and the second leg of the auxiliary bimetal strikes andpulling the operating mechanism of the `movable contact over center,thereby opening the cooperating contacts.

The present invention relates to an ambient temperature compensatedoverload relay, and more particularly to such a relay having anauxiliary thermal element for keeping constant the distance a Aprimarythermal element within the relay must travel before it opens the relaycontrol circuit, despite changes in the ambient temperature.

The present invention is used in connection with overload relays of thetype shown in U.S. Patent No. 3,226,510 issued to R. W. Thomas, et al.,on Dec. 28, 1965, and assigned to the assignee of the instant invention.Such overload relays are, in turn, used in connection with, and toprotect, electrical apparati such as the motor starter shown in U.S.Patent No. 3,324,431, issued June 6, 1967 which is assigned to theassignee of the instant invention. In such overload relays there is acontrol circuit which is comprised of a stationary contact and of amovable contact, with the latter being mounted on a pivotally mountedarm. The arm forms one leg of a toggle. A biasing means or spring formsthe other leg `of the toggle. The contact arm can be constructed in sucha manner that it is pivoted at a control point and carries the movablecontact at one end.

A heater is provided in the vicinity of a primary thermal element whichImay be a bimetallic strip.

As the 2t (where z' is the amperage and t is the time) through thecircuit containing the heater increases, the heat generated by theheater correspondingly increases and the temperature in the vincinity ofthe thermal ele- `ment rises correspondingly. The primary thermalelement ICC deflects in an amount corresponding to the change intemperature in its vicinity.

A translator bar is provided which is in engagement with the primaryelement and is moved by the deflection of the thermal element.

The movable contact arm, or preferably, the biasing spring, are inengagement with the translator bar in such a manner that movement of thebar over a predetermined distance will cause the movable contact toseparate from the stationary contact, thereby opening the controlcircuit. The biasing spring has a center line position, at whichposition it is at its greatest extension. When it is moved beyond thecenter line in one direction, the spring pulls the movable contact awayfrom the stationary contact. When the spring is moved beyond the centerline in the opposite direction, the spring snaps the movable contactagainst the stationary contact. The relay can be calibrated to adjustthe position of the center line and thereby to adjust the predetermineddistance the biasing spring must be moved before the movable contact ispulled from -the stationary contact.

As long as the ambient temperature remains constant, the position of theprimary thermal element, prior to its deflecting due to a higher levelcurrent passing through the heater circuit, will always be the same.

However, if the ambient temperature increases, the primary thermalelement will have deflected to some extent independent of thetemperature of the heater. Since the calibration of the relay isdetermined by the total heat imparted to the primary thermal element,including the :2t heat generated in the heater circuit, a lesserincrease in the time-current passing through the heater circuit maycause the primary thermal element to deflect a sufficient additionalamount, in addition to the deflection due to change in ambienttemperature, to cause the movable contact to separate from the thestationary one.

Similarly, if the ambient temperature decreased, the pri-mary thermalelement will have -deflected in the opposite direction, independent ofthe heat generated by the heater. In this case, a greater increase inthe time-current passing through the heater circuit will be necessary tocause the primary thermal element to deflect a sufficient amount, whenthe deflection due to the decrease in ambient temperature is subtracted,to cause the movable contact to separate from the stationary one.Obviously, if the relay is calibrated properly for one ambienttemperature, and if the ambient temperature changes, the relay will nolonger be properly calibrated.

A means is, therefore, needed to ensure that for variation in theambient temperature, the primary thermal element will deflect thepredetermined distance based on a predetermined amount of heat generatedby the heater circuit before causing the control circuit to open.

The present invention provides an axuiliary thermal element whichdeflects in response to changes in the ambient temperature and which, byso deilecting, maintains a constant predetermined distance of travel forthe primary thermal element to open the control circuit.

The auxiliary thermal element of the present invention may be generallyU-shaped. The deilecting leg of the U-shaped thermal element engages aformation on the translator bar. The other or non-deflecting leg ispositioned near an abutment portion of the relay. The nondeflecting legof the auxiliary thermal element is the structure which causes theseparation of the movable and stationary contacts when it is operatedagainst the biasing means or spring.

By employing an auxiliary thermal element, only the increase in the heator time-current of the heater will be effective to cause the primarythermal element to separate the contacts of the control circuit.Deflection of the primary element due to an increase of the heatgenerated by the heater pulls the translator bar, which, in turn, pullsthe deilectable leg of the auxiliary element, which is in engagementwith the translator bar. The auxiliary element is pivotally secured atthe base of its U to the relay housing. As the deectable leg of theauxiliary element is pulled by the translator bar, the auxiliary elementpivots about its support.

The non-deecting leg of the auxiliary element also pivots and is broughtinto engagement with the biasing means. Continued deflection of theprimary element causes that leg of the auxiliary element to push thebiasing means suiciently to cause separation of the movable contact fromthe stationary contact.

The auxiliary thermal element may be a bimetallic strip. Since it isU-shaped, its legs deilect in opposite directions in response tovariations in ambient temperature. For example, upon an increase in theambient temperature, the legs of the U deflect outward and upon adecrease in the ambient temperature, they deiect inward.

An increase in the ambient temperature, which would ordinarily causeboth legs of the U to move outward, will cause only the leg of the Uengaged with the translator bar to move, since the other leg isprevented from moving by the abutment portion of the relay. The outwardmovement of the leg of the auxiliary element repositions the translatorbar. The primary element will have also deflected in response to theincrease in ambient temperature. However, since it will have deflectedto the same extent that the deecting leg of the auxiliary element hasdeflected, looking at the primary element from the vantage point of thetranslator bar, the primary element will not have deected at all.

A decrease in the ambient temperature would ordinarily cause both legsof the U to move inward. As the deecting leg of the auxiliary elementmoves inward, it draws the translator bar along with it and repositionsit. The non-deilecting leg of the auxiliary element moves inward aslight amount until it comes into engagement with the biasing meansconnected to the movable contact. The biasing means blocks furtherinward movement of the non-deflecting leg of the auxiliary element.Normally, the force being exerted by the non-deflecting arm on thebiasing means might be sufficient to cause the biasing means to move andseparate the movable contact from the stationary one. However, theauxiliary thermal element is pivotally mounted at its base to the relayhousing. Thus, while the non-deilecting leg is held still by the biasingmeans, the deflection which would normally take place in thenon-deilecting arm is reflected in pivoting of the auxiliary element atthe base of its U, which increases the deflection of the deecting arm ofthe auxiliary element. The primary element will have deected in the samedirection over the same distance as the deecting arm of the auxiliaryelement due to the decrease in the ambient temperature. Hence, lookingat the primary element from the vantage point of the translator bar, theprimary element will not have deflected at all. l

In view of the foregoing, the biasing means will not be aifected by therepositioning of its translator bar due to changes in the ambienttemperature. Consequently, when the primary thermal element deects dueto a change in the current passing through the heater circuit, theprimary thermal element must still be deflected the predetermineddistance to move the non-deflecting arm of the auxiliary element thesame predetermined distance to cause the separation of the movable andthe stationary contacts in the manner set out above.

Thus, this invention ensures that dellection of both the primary andauxiliary thermal elements due to changes in the ambient temperaturewill not affect the distance the primary thermal element must travelbefore it will cause the separation of the movable and stationarycontacts. Furthermore, the primary element will always deect apredetermined distance, due to heating of the heater, be-

fore it causes separation of the contacts in the control circuit,regardless of the ambient temperature.

Accordingly, it is a primary object of the present invention to providean ambient temperature compensated overload relay with a means forcompensating for changes in the ambient temperature, thereby ensuringthat the control circuit of the relay will not open until apredetermined heat is generated by the heater circuit of the v relay.

It is another object of the present invention to provide such an ambienttemperature compensated overload relay wherein the auxiliary thermalelement, by compensating for changes in ambient temperature, calibratesthe relay so that the primary thermal element must always travel apredetermined distance before opening the control circuit.

It is a further object of the present invention to provide such a relaywherein the auxiliary thermal element participates in the opening of thecontrol circuit after a predetermined current passes through the heatercircuit.

It is another object of the present invention to provide such a relaywhere compensation for ambient temperatures is accomplished byrepositioning the motion translator bar connecting the primary thermalelement and the movable Contact of the control circuit.

It is another object of the present invention to provide such a relaywherein the auxiliary thermal element is pivotally mounted and isU-shaped, having a deflecting and a non-deflecting arm, wherein thedeflecting arm repositions a translator bar engaged with the primarythermal element due to changes in ambient temperature and thenon-deflecting arm is employed to cause the movable contact to separatefrom the stationary contact.

These an-d other objects of the present invention will become apparentwhen the following -description is read in conjunction with theaccompanying drawings, in which:

FIGURE 1 is a cross-section of an ambient temperature compensatedoverload relay according to the present invention;

FIGURE 2 is a view of the translator bar used in conjunction with theinstant invention viewed in the same direction of view as that of FIGURE1;

FIGURE 3 is a view in a direction 3-3 of FlG- URE 2; f

FIGURE 4 is a side View of the auxiliary thermal element lshown inFIGURE 1; and

FIGURE 5 is a view of the auxiliary thermal element of the instantinvention as viewed in the direction 5--5 of FIGURE 1.

Referring4 to the drawings, the present invention is used in connectionwith an overload relay, e.-g., of the type described in U.S. Patent No.3,226,510.

The housing 7 of an overload relay is divided by a wall or dividingstructure 8 into a heater chamber 9 and an ambient temperaturecompensation chamber 10.

Within the ambient temperature compensation chamber is a controlcircuit, which extends from terminal 11 through terminal strap 12,through movable contact support arm 13, through movable contact 14,through stationary contact 15, through terminal strap 16, and finallythrough terminal 17. Ar-m 13 is a rigid element supported at its end 18in a formation on strap 12 which permits the arm 13 to pivot about itsend 18.

Biasing means 19, which is connected by hook 20 at one of its ends toarm 13, and by hook 25 at its other end to support 21, biases contact 14against contact 1S. Biasing means 19 can be a tension spring. There is acenter line 22 at which the biasing means is at its greatest extension.If the means 19 is urged in direction A beyond the center line, theimeans 19 snaps the movable contact 14 open to its dotted line positionof FIGURE 1 abutting surface 23 which can ybe a part of housing 7. Thenow open movable contact 14 can be moved lback into contact with thestationary contact 15 by slide 60 ina manner described in Patent No.3,226,510.

Adjustment of support means 21, by turning its head 26, causes the means21 to move alternatively in direction A or in the opposite direction C,since the surface 24 of the means 21 has threads which mesh with athreaded aperture in terminal strap 12. Adjustment of means 21repositions the center line 22 and adjusts the over center position ofarm 13.

When the control circuit is closed, as is shown in solid lines in FIGURE1, a circuit is closed to, e.g., the starter coil of a motor starter,such as that shown in U.S. Patent No. 3,324,431, issued June 6, 1967; ora signaling device. When the control circuit is opened, the circuit isbroken. The opening of the control circuit might automatically orsimultaneously close an indicatin-g or a second control circuit in amanner shown in U.S. Patent No. 3,226,510.

Within the heater chamber 9 is a heater 27, which can be congured in anynumber of ways, as shown in U.S. Patent No. 3,226,510, providing heat tothe heating chamber. The heater has terminals 28 and 29 to which leadsfrom the circuit, into which the overload relay is inserted, can beconnected, thereby completing a heater circuit.

The control circuit is intended to respond to variations in the i2tpassing through the heater. In the embodiment of the present inventionshown in FIGURE 1, the control circuit is designed to respond to anincrease in the zt through the heater 27 beyond a predeterminedthreshold valve.

Accordingly, some means is required so that when the time-currentrelation or heat in the heater 27 reaches a predetermined thresholdvalue, the control circuit will be opened. A primary thermal element 30,which is mounted at its end 31 to a support means 32, as is more fullydescribed in U.S. Patent No. 3,226,510, is provided. The element 30:might be a bimetallic strip comprised of two face-bonded strips ofmetal having dilierent coefcients of expansion.

In FIGURE 1, the primary element 30 is indirectly heated by the heater27. An alternate embodiment (not shown) of the present invention has theprimary element being directly heated by having the primary elementserve as part of the means electrically connecting between terminals 28and 29.

As shown by the dotted lines in FIGURE l, when the heat in chamber 9increases, the free end 33 of element 30 dellects in direction A.

Primary thermal element 30 engages translator bar 40 by `abuttingsurface 41 of projecting ear 42 (see FIGURE 3). The bar 40 will,therefore, move in direction A through the same distance as the free endof element 33.

The bar 40 has in engagement with it the auxiliary thermal element 50(see FIGURE 4). Auxiliary element 50 is. as can be seen in FIGURE 4,generally U-shaped, having arms 51 and 52. The base 53 of the element 50is secured to the housing 7 by la support means 54, which permits theelement 50 to pivot thereabout in a manner described hereinbelow. Thesupport means 54 might be a hinge or might be comprised of a flexibleconnectin-g material. Aperture 57 in the arm 52 of the auxiliary thermalelement is provided so that support means 21 can be connected with thebiasing means 19 while the means 21 is externally adjustable.

The auxiliary thermal element 50, like the primary element 30, should beso comprised that its arms deflect, due to changes in the ambienttemperature. The element 50 can be a bimetallic strip comprised ofsimilar materials and in a similar manner as the primary element 30. Asthe ambient temperature increases, the element 50 tries to move toward astraight line condition, i.e., the arms 51 and 52 press outward. As theambient temperature decreases, the arms 51 and 52 deflect inward towardone another.

The notch 43 of the translator bar 40 provides a formation for engagingportion 55 of arm 51 of element 50. Thus, when translator bar 40 movesin direction A in response to dellection in that direction by primaryelement 30, due to an increase in the amperage in the heater circuit,arm 51 of the auxiliary element is pulled in the same direction. Sincethe auxiliary element is secured by support means 54, heater-causedmovement of the arm 51 causes the entire element 50 to pivot indirection B about its support means 54. This causes arm 52 and itsactuating portion 56 to be moved in direction B.

Pivoting actuating portion 56 of auxiliary terminal element 50 engagesthe biasing means 19 and pushes the same in the direction B. When thebiasing means 19 has been pushed over the center line 22, the movablecontact 14 snaps open to its dotted line position of FIGURE l.

The foregiing described the manner in which the heating of the heater 21causes the separation of the movable contact 14 from the stationarycontact 15, thereby opening the control circuit.

A problem can arise in the calibration of the overload relay describedabove when changes occur in the ambient temperature. Once the positionsof the biasing means 19 and of the center line 22 have been set byadjustment of the support means 21, separation of the movable contact 14from the stationary contact 15 will occur only after the translator bar40 has been moved a predetermined distance in the direction A. Movementof the translator bar 40 is controlled Iby deflection of the primarythermal element 30. If, for example, the ambient temperature within thehousing 7 has increased, even before the heater 21 has heated up inresponse to an increase in the current in the heater circuit, theprimary thermal element will have deflected a distance in the directionA. Thus, the end 33 of the primary element 30 will have to deflect ashorter distance in the direction A as a result of an increase of theheat generated by the heater 21 before it causes the opening of thecontrol circuit. Obviously, at elevated ambient temperatures, a lesserincrease in the current passing through the heater 21 will cause aseparation of the contacts in the control circuit than at lower ambienttemperatures.

If, on the other hand, the ambient temperature within the housing 7 hasdecreased, the primary thermal element 30 will have deected a distancein the direction C. Thus, when the heater 21 has heated up in responseto an increase in the current in the heater circuit, the end 33 of theprimary element will have to deflect not only the predetermined distanceit was calibrated to deflect, but the additional distance that theprimary element had previously deected in direction C due to a decreasein the ambient temperature. Obviously, as the ambient temperaturedecreases, a greater increase in the current passing though the heater21 will be required to cause a separation of the contacts in the controlcircuit than at higher ambient temperatures.

The auxiliary element 50 of the present invention is designed tocompensate for changes in the ambient temperature. As was noted above,the arm 51 of the element 50 is positioned within notch 43 of thetranslator bar 40. The arm 52 of the element 50 is normally positionedbetween the biasing means 19 and the abutment surface 61 of the terminalstrap 12. Neither the arm 52 nor its actuating portion 56 is inengagement with the translator bar 40. This is ensured by the cut-outportion 44 of the translator bar 40.

When the ambient temperature increases, the arm 51 of the auxiliaryelement dellects in direction A. The arm 52 attempts to deflect indirection C, which is opposite to direction A. However, the abutmentsurface 61 prevents movement of the arm 52 in direction C. Consequently,the outward movement of the arm 52 is translated into pivotal movementof the base 53 of the auxiliary element 50 about its support 54 in thedirection B, which causes the arm 51 to move an additional distance inthe direction A.

The materials of which the primary element 30 and the auxiliary element50 are comprised can be so chosen by one skilled in the art, and theprimary and auxiliary elements can be so positioned, that for everychange in the ambient temperature, whether it be an increase ordecrease, the defiection of both the end 33 of the primary element 30and of the leg 51 of the auxiliary element 50 will be in the samedirection and will be equal in distance.

Deflection of the primary thermal 'element 30 and of the arm 51 of theauxiliary thermal element 50 due to an increase in the ambienttemperature moves the translator bar 40 inthe direction A the samedistance as each element defiects. However, the arm 52 of the auxiliarythermal element, being in engagement with abutment surface 61, hasdeflected only minimally. Thus, even after the translator bar 40 hasbeen moved by both thermal elements in response to an increase in theambient ternperature, the bar 40 must still be moved the predetermineddistance in order to cause the portion 56 of the auxiliary thermalelement to move the biasing means 19 suflciently to separate the contact1S from the-contact 14.

Upon a decrease in the ambient temperature, the arms 51 and 52 of theauxiliary element 50 move toward one another. After the arm 52 has moveda short distance in the direction A, portion 56 will engage the biasingmeans 19. Further defiection inward of the arm 52 would nor` mally movethe biasing means in the direction Aand might cause the means 19 to moveover the center line 22, thereby opening the movable contact 14.However, because of the pivotal mounting of the base 53 on support means54, instead of the arm 52 continuing to move in the direction A, furtherdeiiection in that direction causes the base 53 to pivot in thedirection D. The arm 51 of the element 50, meanwhile, is defiectinginward in the direction C. The pivoting of the base 53 in the directionD increases the amount of pivoting done by the arm 51.

Due to the pivoting of the base 53, the portion 56 does not bear on thebiasing means 19 with sufiicient pressure to cause it to move and,therefore, there is no danger that the movable contact will be forcedopen when the ambient temperature is decreasing.

Movement of the arm S1 in the direction C repositions the translator bar40. The end 33 of the primary element 30 is also defiected in thedirection C due to the decrease in the ambient temperature. As was notedabove, the materials of the primary and auxiliary elements are so chosenthat the distance that the end 33 and that the arm 51 deflects is thesame for each decrease in the ambient temperature. Thus, even after thetranslator bar 40 has been moved by the arm 51 of the auxiliary thermalelement in response to a decrease in the ambient temperature, the bar 40must still be moved the predetermined distance in direction A by anincrease in the temperature of the heater 27 in order to cause theportion 56 of the auxiliary thermal element to move the biasing means 19sufficiently to separate the contact 15 from the contact 14.

From the foregoing, it can be seen that the invention has provided anovel thermally actuated overload relay with a control circuitcomprising a movable and a stationtionary contact in which the movablecontact will be separated from the stationary contact after there hasbeen a predetermined change in the heat generated by the heater circuit,regardless of the ambient temperature within the relay housing.

Although there has been described a preferred embodiment of this novelinvention, many variations and modifications will now be apparent tothose skilled in the art. Therefore, this invention is to be limited notby the specific disclosure herein, but only by the appending claims.

The embodiments of the invention in which an exclusive privilege orproperty is claimed are defined as follows:

1. In an ambient temperature compensated overload relay, said relaycomprising:

a housing;

cooperating contacts in a first circuit through said relay; saidcontacts being within said housing and including a relatively stationaryand a relatively movable contact; terminals to which saidcontacts areconnected; 1

a heater which is positioned and adapted to be heated by the 2t in asecond circuit through the overload relay;

a primary bimetal within said housing and positioned with respect tosaid heater as to be heated when said heater heats up; support meanswithin said housing for mounting said primary bimetal; said primarybimetal having the characteristic that va first end thereof defiects asboth the heat generated by the z'2t to the circuit and the ambienttemperature increase and decrease;

a translator bar means; l

a first formation on said translator bar means; said first endl of saidprimary bimetal being engageable with said first formation as saidprimaryy bimetal deflects in a first direction;

an auxiliary bimetal within said housing positioned away from saidheater, whereby said auxiliary bimetal can res-pond to theambienttemperature in said housing without being directly affected by heatingof said heater; s aid auxiliary bimetal including a first and a secondleg joined by a web;

a second formation on said translator bar means; said first leg of saidauxiliary bimetal being in engagement with said second formation as saidauxiliary bimetal deflects, for shifting said translator bar means inresponse to ambient temperature variation;

said translator bar means being linked to said movable contact so thatmovement of said translator bar means due to deflection of said primarybimetal as a result of an i2l overload will cause said cooperatingcontacts to separate;

the improvement comprising,

pivot support means in said housing for supporting said auxiliarybimetal by said web thereof and for permitting said auxiliary bimetal topivot as described; said web being pivotally supported on said pivotsupport means therefor;

blocking means in said housing for blocking movement of said second legof said auxiliary bimetal, whereby defiection of said auxiliary bimetaldue to variations in the ambient temperature in said housing causesdeflection of said first leg of said auxiliary bimetal and causespivoting of said web of said auxiliary bimetal about said pivot supportmeans.

2. In the ambient temperature compensated relay of claim 1, said relayfurther comprising first means for separating said relatively movablecontact from said relatively stationary contact, said rst means beingpositioned to be acted upon and being connected with said translator barmeans; the improvement further comprising:

said blocking means comprising an abutment surface in said housing whensaid auxiliary bimetal is defiecting in one direction and comprises saidfirst means when said auxiliary bimetal is defiecting in the oppositedirection.

3. In the ambient temperature compensated relay of claim 1, theimprovement further comprises, said first means for separating saidrelatively movable contact from said relatively stationary contact ispositioned so as to be engaged by said second leg of said auxiliarybimetal;

upon deiiection of said primary bimetal due to an izt overload and uponcorresponding shifting of said translator bar means, said first leg ofsaid auxiliary bimetal being correspondingly shifted by` said translatorbar means; said pivot support means for said auxiliary bimetalpermitting said auxiliary bimetal to pivot thereabout to cause saidsecond leg of said auxiliary bimetal to engage said first means and tripapart said cooperating contacts.

4.' In the ambient temperature compensated relay of claim 3, said firstmeans comprises an over center tension spring stretched between saidrelatively movable contact and a fixed support on said housing.

5. In the ambient temperature compensated relay of claim 3, theimprovement further comprises said blocking means comprising an abutmentsurface in said housing when said second leg of said auxiliary bimetalis deflecting in one direction, and comprising said first means forseparating said relatively movable contact from said relativelystationary contact when said second leg of said auxiliary bimetal isdeecting in the opposite direction.

6. In the ambient temperature compensated relay of claim 5, saidauxiliary bimetal being U-shaped and having the characteristic of havingits legs deect ioutward on one of ambient temperature increase anddecrease, and deflect inward on the other of the increase and decrease;on said auxiliary bimetal deecting outward, said second leg thereofcontacting said housing abutment surface; and on said auxiliary bimetaldefecting inward, said second leg thereof contacting said first means.

7. In the ambient temperature compensated relay of claim 6, said firstmeans comprises an over center tension spring stretched between saidrelatively movable contact and a fixed support on said housing.

8. In the ambient temperature compensated relay of 25 10 claim 7, saidprimary and auxiliary bimetals being constructed and positioned todeflect in the same direction due to variations in temperature;

said auxilary bimetal being designed whereby the portion of said firstleg thereof that engages said translator bar means deects the samedistance as the end of said primary bimetal that engages said translatorbar means; upon an increase in the ambient temperature, said arms ofsaid auxiliary bimetal deflect outward; and upon a decrease in ambienttemperature, they defiect inward.

References Cited UNITED STATES PATENTS 2,851,556 9/1958 Van Valkenburg200-116 3,226,510 12/1965 Thomas et al.

3,213,243 10/1965 Anderson et al.

BERNARD A. GILHEANY, Primary Examiner. R. COHRS, Assistant Examiner.

U.S. C1. X.R.

